import com.fasterxml.jackson.databind.ObjectMapper;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    private ObjectMapper objectMapper=new ObjectMapper();
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf8");
        resp.setCharacterEncoding("utf8");
        //1.获取请求中的参数
        String username=req.getParameter("username");
        String password=req.getParameter("password");
        System.out.println("username="+username+",password="+password);
        if(username == null || "".equals(username) || password == null || "".equals(password)){
            //请求内容缺失，登录失败
            resp.setContentType("text/html;charset=utf8");
            resp.getWriter().write("当前的用户名或密码为空");
            return;
        }
        //2.和数据库中的内容进行比较
        UserDao userDao=new UserDao();
        User user=userDao.selectBYName(username);
        if(user == null || !user.getPassword().equals(password)){
            //用户没有查询到或者密码不匹配，也是登录失败
            resp.setContentType("text/html;charset=utf8");
            resp.getWriter().write("当前的用户名或密码错误");
            return;
        }

        //3.如果比较通过，创建会话
        HttpSession session =req.getSession(true);
        session.setAttribute("user",user);
        //4.返回一个重定向报文，跳转到博客列表页
        resp.sendRedirect("blog_list.html");

    }

    //这个方法就让前端来检测当前的登录状态
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       resp.setContentType("application/json;charset=utf8");
        HttpSession session= req.getSession(false);
        if(session == null){
           //检测下会话是否存在，不存在说明未登录
           User user=new User();
           resp.getWriter().write(objectMapper.writeValueAsString(user));
           return;
       }
        User user = (User) session.getAttribute("user");
        if(user == null){
            // 虽然有会话，但是会话里没有user对象，也视为未登录
            user = new User();
            resp.getWriter().write(objectMapper.writeValueAsString(user));
            return;
        }
        //已经登录的状态
        //此处不能把密码返回给前端
        user.setPassword("");
        resp.getWriter().write(objectMapper.writeValueAsString(user));


    }
}
